To give ion conductivity to an electrolyte membrane, a reactant gas to be supplied to a polymer electrolyte fuel cell is humidified by, for example, a humidifier. However, depending on a temperature environment at the time of electric power generation, condensed water is generated in the reactant gas. In a case where droplets of the generated condensed water are accumulated in the fuel cell, the supply of the reactant gas is interfered, and an abnormal voltage reduction may occur.
To solve this problem, known is a fuel cell system in which a pipe coupled to a fuel cell stack is provided with an inclined portion that is inclined upward toward the fuel cell stack (see PTL 1, for example). Also known is a fuel cell system which includes a fuel cell stack body and a gas introducing portion extending in an end plate and communicating with a gas supply manifold and in which the gas introducing portion in the end plate is inclined downward from a side facing the gas supply manifold toward an upstream side of the flow of the reactant gas in the gas introducing portion (see PTL 2, for example).
In the fuel cell system disclosed in PTL 1 or 2, the pipe or the gas introducing portion is inclined, so that the condensed water generated in the pipe or the like is prevented from being supplied to the manifold.
Further known is a polymer electrolyte fuel cell in which a lowermost portion of a portion communicating with an inlet-side manifold of a gas channel is located above a gas supply pipe in the direction of gravitational force, the gas supply pipe being connected to the inlet-side manifold (see PTL 3, for example). In the polymer electrolyte fuel cell disclosed in PTL 3, even in a case where the condensed water is mixed in the reactant gas supplied to a stack, the condensed water is temporarily accumulated at a bottom portion of the manifold, so that the condensed water can be prevented from being selectively supplied to a specific cell (cell close to the gas supply pipe side).